Ties are broken as follows:
1) Owners Points
2) Best finishes, most wins, 2nds, 3rds and so on until the tie is broken
3) If tie still remains, then the team with the highest position first breaks the tie
(so if two are ties, both have a win, then the team who won first gets the spot)

From NASCAR Integrated Marketing Communications with updates, corrections updated when found out.

SOME PROCEDURES and RULES NOTES about Qualifying

NASCAR's Competition Department distributes entry blanks for each race to owners in the series.
Those entries must be returned before the deadline, which is set 13 days in advance of the event.
When the entry is received by Competition, the car is added to the entry list.
There is an inspection fee for each entry.